Laboratory for Research in Advanced Rock Engineering

Our Vision: Rock Engineering Redefined ™

Modern mining industry faces new challenges: lower ore grades, increased variability within ore bodies, and fluctuating commodity prices. All of those impact projects profitability. The Laboratory for Research in Advanced Rock Engineering at the University of British Columbia (UBC) adopts modern field data techniques, laboratory testing and state-of-the-art numerical tools that allow integrating geological and rock mechanical information in a predictive model essential for short and medium-term planning. Our research focus on:

Challenges in the characterization of intact rock bridges in rock slopes

Analysis of fragmentation processes

Design of rock foundation anchorage

Modelling of blast-induced damage

Facilities and Equipment

Our graduate students have access to state-of-the-art numerical codes, workstations for advanced numerical modelling and a modern rock mechanics laboratory equipped with an MTS-85 for uniaxial/triaxial testing, a GCTS DS-100 for direct shear testing, a GCTS-PLT110 for point load testing, and a GCTS-75 Grinder and Saw for rock samples preparation. In the last 5 years we have invested more than $160,000 to purchase new equipment and maintain software licenses. Our rock mechanics lab is equipped with the following testing devices. The equipment is available on request for commercial testing.

Our research group includes a mix of domestic and international students, which are passionate about their research and work hard to contribute to important advances in the field of rock engineering. Our graduate students receive training related to state-of-the-art numerical modelling, laboratory experimentation and instrumentation, and field data collection. Currently we have 3 full time PhD students and 4 full time MASc students.

We welcome collaboration with other institutes and universities in Canada, North America and worldwide. 2 visiting PhD candidates (University of Science & Technology, Beijing, China; University of Chile, Santiago, Chile) just completed a 12 months study visit with us. 2 PhD candidates from the University of Bologna (Italy) and the University of Siena (Centro di Geotecnologie, Italy), and 1 MASc candidate from the Politecnico di Torino (Italy) completed exchange programs with us in 2017 and 2016, respectively. Former graduate students include 5 MASc students (direct supervision) and 3 PhD students (direct supervision and co-supervision).

Rock engineering design requires quantitative measurements of rock mass properties. Quantification of rock mass quality holds many challenges: rock masses are spatially variable, and their quality cannot be realistically described by a single averaged rock mass rating. There is the need to develop classification methods that use direct measurements of intact rock and discontinuities properties rather than qualitative and semi-quantitative ratings. Our research team employs discrete fracture network (DFN) models as effective tools for the characterization of rock masses by using statistical distributions to generate realistic three-dimensional (3D) representations of natural fracture networks, that also account for the spatial variability of fracture intensity and joint roughness/alteration conditions.

Example of the use of DFN models to study the correlation between rock quality designation (RQD) and Geological Strength Index (GSI) for varying fracture frequency (P10).

Example of the use of DFN models to show how the estimated rock mass quality (GSI) for a large-scale slope problem would vary depending on the modelling assumptions (Miyoshi et al., 2018)

In the past decade the synthetic rock mass (SRM) approach has been increasingly used for simulating the mechanical behaviour naturally fractured rock masses. Three main components converge into the SRM approach: i) data collection and characterisation, ii) discrete fracture network (DFN) modelling, and iii) the geomechanical model used for simulating rock mass behaviour, and combining the effects of intact rock fracturing and failure occurring along the natural fractures. The use of a SRM modelling approach has several benefits; for instance, SRM modelling results allow the definition of equivalent Mohr-Coulomb or Hoek-Brown strength envelopes, and fully account for anisotropic effects and rock mass scale effects.

Challenges in the characterisation of intact rock bridges in rock slopes

The importance of intact rock bridges and step-path geometries in both engineered and natural rock slopes has been recognised for almost five decades; notwithstanding, reliable estimates of rock bridge percentages and the magnitude of rock bridge strengths to assume in slope analyses remains a major challenge. Any attempt to measure rock bridges is exacerbated by the fact that rock bridges are not visible unless the rock mass is exposed by human activities or by natural events. Human activities (e.g. blast induced, and excavation induced fractures) may further complicates the definition and measurement of rock bridges. To allow further advances in rock bridge research, we recognize the importance of an integrated state-of-the art characterisation, numerical modelling, and slope monitoring approach emphasising the control of fracture network connectivity on both measured and simulated rock slope performance. Our research aims to provide better definitions and measurement of rock bridges. Our research have proposed a unified system of rock bridge intensity measures that provide an easy framework to move between differing scales and dimensions (RBij) that combines the dimensions of the sample and the dimensions of the measurement.

The fragmentation produced in the orebody during the caving process controls the overall success and profitability of a block caving operation; however, fragmentation is extremely difficult to measure reliably and routinely. Advanced numerical analysis is used to simulate the processes of rock breakage that are expected to occur inside an ore column in a block cave mine. The proposed approach is capable of simulating crushing and abrasion between rock blocks in a realistic manner. The approach is also capable of reproducing hangs-ups and stable arching conditions that might be encountered at the drawpoints in a block cave mine.

Example of numerical analysis of fragmentation processes and draw for a single drawpoint.

Example of numerical analysis of fragmentation processes and draw for a multiple drawpoints.

A major consideration in the design of high capacity tiedown anchors for dam, bridge and tower foundations is the tensile resistance of the rock mass to pullout, typically as a result of overturning moments or hydrostatic uplift. Rock mass pullout capacity for installed anchors is developed from the tensile strength and fracture propagation properties of intact rock, the orientation and physical properties of the discontinuities and anchor confinement at depth. The typically assumed, but generally conservative, design approach is to calculate anchor pullout capacity using the dead weight of a uniformly shaped inverted “cone” with an assumed initiation point and breakout angle. As an alternative to the current foundation anchor design method, Discrete Fracture Networks (DFN) combined with numerical simulations can be used in attempt to reduce the uncertainty inherent in the design of rock anchors.

Our research group have successfully applied hybrid finite-discrete element methods to study blast-induced damage in circular tunnels. An extensive database of field tests of underground explosions above tunnels is used for calibrating and validating the proposed numerical method; the numerical results are shown to be in good agreement with published data for large-scale physical experiments. The method is then used to investigate the influence of rock strength properties on tunnel durability to withstand blast loads. To date the analysis has considered blast damage in tunnels excavated through relatively weak (sandstone) and strong (granite) rock materials. It was found that higher rock strength will increase the tunnel resistance to the load on one hand, but decrease attenuation on the other hand. Thus, under certain conditions, results for weak and strong rock masses are similar.

Miyoshi T., D. Elmo and S. Rogers. 2017. Influence of data characterization process on the kinematic stability analysis of engineered slopes using discrete fracture network models. Proceedings of the 15th International Conference of the International Association for Computer Methods and Geotechnics. Wuhan, China, October 2017.

Elmo D., T. Miyoshi, H. Sun and A.B. Jin. 2017. An FEM-DEM numerical approach to simulate secondary fragmentation processes. Proceedings of the 15th International Conference of the International Association for Computer Methods and Geotechnics. Wuhan, China, October 2017.

Hamdi P., D. Stead and D. Elmo. 2017. A review of the application of numerical modelling in the prediction of depth of spalling damage around underground openings. In Proceedings of the 51st Int. Symp. Rock Mech., San Francisco, U.S. June 2017. Paper 778.

Rogers S., D. Elmo, G. Webb and G.M. Moreno. 2016. DFN Modelling of major structural instabilities in a large open pit for end of life planning purposes. 50th U.S. Rock Mechanics Symposium. Houston, Texas, June 2016. Paper 882.

Hamdi P., D. Stead and D. Elmo. 2014. Characterizing the influence of micro-heterogeneity on the strength and fracture of rock using an FDEM-nDFN approach. ISRM Rock Mechanics Symposium. 27th to 29th May, Vigo, Spain. (Conference award for the best paper written by a PhD student, Hamdi P.)